REESTABLISHMENT AND RESURGENCE OF PLANT-PARASITIC NEMATODES IN FUMIGATED PINEAPPLE FIELDS AT DIFFERENT ELEVATIONS AND IRRIGATION REGIMES INHAWAII

Introduced or remnant populations of Meloidogyne javanica, Rotylenchul us reniformis, Helicotylenchus dihystera and Paratylenchus spp. in Haw aiian pineapple fields located at three elevations or subjected to two irrigation regimes were monitored following soil fumigation. Introduc ed populations of M. javanica established more readily at high-elevati on than lower-elevation sites, and resident populations of Helicotylen chus, Rotylenchulus and Paratylenchus resurged readily at lower- but n ot at high-elevation sites. Despite variations in number of M. javanic a introduced initially, resident as well as introduced nematodes multi plied subsequently to various specific levels at different localities. Generally, population densities of M. javanica and resident nematodes at a particular site were higher at time of ratoon- than plant-crop h arvest, and In irrigated than non-irrigated plots. Fruit yields of the ratoon-crop were equal to or lower than the plant-crop, and were more affected in irrigated than in non-irrigated plots. Site location, irr igation and time of crop harvest were important factors influencing th e rate as well as the final level of a nematode population build-up. T he feasibility of exploiting these factors for nematode control should be further studied.